Germany's Vice Chancellor Sigmar Gabriel warned Saudi Arabia on Monday Berlin could review military exports to the oil-rich nation in light of Riyadh's mass executions of prisoners two days earlier.

Berlin also urged Saudi Arabia and Iran to restore diplomatic relations after 47 people were executed, including a Shiite cleric, which sparked attacks on the Saudi embassy in mainly Shiite Iran followed by a severing of official ties between the regional powers.

Gabriel, who is also Germany's economy minister, said: "We must now review whether in future we should take a more critical stance on defensive armaments which we have so far sold to Saudi Arabia for its national defence."

"It turns out we were right not to deliver battle tanks or G36 assault rifles to Saudi Arabia," he added, national news agency DPA reported.

Germany has refrained from selling the Heckler & Koch G36 assault rifle and other offensive military weapons to Saudi Arabia but has shipped millions of euros worth of so-called defensive military gear.

Exports last year included patrol boats, all-terrain vehicles, aerial refuelling equipment, drones and parts for combat aircraft and armoured vehicles, said national news agency DPA.

A spokesman for the economy ministry earlier said it was "following developments" in Saudi Arabia, and that they would "come into play" when it decides on approval for future defence exports to the country.

Chancellor Angela Merkel's spokesman Steffen Seibert called on both Saudi Arabia and Iran "to use all means at their disposal to improve their diplomatic relations".

He said Saudi-Iranian ties are "of fundamental importance for resolving the crises in Syria and Yemen and for the stability of the entire region".

Germany's opposition Greens and Left parties demanded the government halt all military exports to Saudi Arabia, which reached 209 million euros ($226 million) in 2014, the last full year for which data is available.

Seibert, asked whether Germany planned to sanction Saudi Arabia, stressed that "it is in the interest of Germany to have dialogue with Saudi Arabia ... We are committed to a constructive relationship with Riyadh."

French Foreign Minister Laurent Fabius meanwhile called for a "de-escalation of tensions" between Riyadh and Tehran, government spokesman Stephane Le Foll said.

"France has an important role in this region as an interlocutor with all the parties," Le Foll said following a cabinet meeting, noting that Iranian President Hassan Rouhani plans to visit Paris in the coming weeks.

Relations between Sunni-ruled Saudi Arabia and Shiite-dominated Iran have been strained for decades.

The oil-rich foes have also been divided over the nearly five-year war in Syria, where Iran is backing the regime, and the conflict in Yemen where a Saudi-led coalition is battling Shiite rebels.

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